A COOPER MINIMUM PHOTOEMISSION-STUDY OF THE AU95PD5 ALLOY

We present the results of a valence band (VB) photoemission study of a AU(95)Pd(5) alloy in a photon energy range covering the Cooper minima of the Pd 4d and Au 5d photoionization cross sections, (hv = 90-280 e V). The spectra show the presence of the Pd 4d-derived virtual bound s tate (VBS) which we find to lie between the Au 5d band and the Fermi l evel with a binding energy of 1.45 eV. The intensity of this peak goes through a minimum at hv = 140 eV. The results are discussed in terms of the spatial distortion of the Pd 4d wavefunction in the alloy. Subt ractions between the alloy and metallic Au spectra at different photon energies reveal marked differences in the Au 5d part of the valence b and. These differences are ascribed to modifications in the density of states caused by the presence of the impurity and to the variation in the photon energy dependence of the cross section of different parts of the VB spectrum.